Rotary couplers are used in coupling rotary dumpers, hoppers, tipplers or wagons (collectively, rotary railcars) to other railcars, including rotary and non-rotary railcars. The rotary coupler allows the rotary car to be unloaded by rotating the entire rotary car in place, track and all, while the rotary car remains coupled to the other railcars. The rotary coupler facilitates in the rotation by providing a connecter that fits within a yoke. Within the yoke, the connector is able to rotate by approximately 360 degrees. In a traditional rotary coupler, the connector and the yoke each have a corresponding bearing surface that is perpendicular to an axis of rotation about which the connector rotates.
A rotary coupler experiences significant forces, in addition to the rotational forces, as the rotary railcar is engaged and pulled along the track. Over time, the combination of the pulling forces and the rotational forces may cause the rotary coupler to fail. One common failure point for a rotary coupler is at the bearing surfaces of the yoke and/or connector.